KR20150038410A - Process for producing ferrite sintered magnet and ferrite sintered magnet - Google Patents

Abstract

The raw material powder satisfying the required range of 1-xy, x, y and z and the molar ratio n in the general formula Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z is calcined , 1.8% by mass or less of SiO ₂ and 2% by mass or less of CaCO ₃ in terms of CaO are added to the calcined body before calcining, and the calcining is carried out at a temperature of 1100 ° C A magnetoplumbite structure (hexagonal crystal) of a hexagonal crystal structure is obtained by setting a temperature raising rate at a firing temperature of 1 占 폚 / min to 4 占 폚 / min and a decreasing rate of temperature at a firing temperature to 1100 占 폚 of 6 占 폚 / , A first grain boundary phase existing between two columnar phases and a second grain boundary phase existing between at least three columnar phases and having an arbitrary cross section , The second grain boundary phase is scattered, and the average area of the second grain boundary phase is less than 0.2 탆 ² ferrite sintering Magnets are manufactured.

Description

TECHNICAL FIELD [0001] The present invention relates to a ferrite sintered magnet and a ferrite sintered magnet,

The present invention relates to a method of manufacturing a ferrite sintered magnet and a ferrite sintered magnet.

Ferrite sintered magnets are used in various applications such as motors, generators, and speakers. As typical ferrite sintered magnets, Sr ferrite (SrFe ₁₂ O ₁₉ ) and Ba ferrite (BaFe ₁₂ O ₁₉ ) having a hexagonal M type magnetoplumbite structure are known. These ferrite sintered magnets are produced at relatively low cost by powder metallurgy using iron oxide and carbonates of strontium (Sr) or barium (Ba) as raw materials.

BACKGROUND ART [0002] Recently, for the purpose of reducing the size, weight, and high efficiency of components in automotive electric parts and parts for electric devices, for reasons such as consideration of environment, high performance of ferrite sintered magnets is required. Particularly, a motor used for an automotive electric component has a high residual magnetic flux density B _r (hereinafter simply referred to as " B _r ") and a strong demagnetizing field ) are not referred to as a high coercive force (保磁力) H _cJ (hereinafter simply referred to as "H _cJ") and a high squareness ratio (角型比) H _k / H _cJ (hereinafter simply referred to as "H _k / H _cJ" ) Is required for the ferrite sintered magnet.

In order to improve the magnetic properties of the ferrite sintered magnet, a method of replacing a part of Sr in Sr ferrite with a rare earth element such as La and substituting a part of Fe with Co to improve H _cJ and B _r Is proposed in Japanese Laid-Open Patent Publication No. 10-149910 and Japanese Laid-Open Patent Application No. 11-154604.

Sr ferrite (hereinafter referred to as " SrLaCo ferrite ") described in Japanese Patent Application Laid-Open Nos. 10-149910 and 11-154604 in which a part of Sr is replaced with a rare earth element such as La, ) Is widely used for various purposes in place of conventional Sr ferrite and Ba ferrite, because of its excellent magnet characteristics, but further improvement of the magnetic properties is also required.

Japanese Patent Application Laid-Open No. 2001-223104 discloses that in order to improve the H _cJ of the SrLaCo ferrite, in the temperature raising process of the firing process, the temperature rise from 900 ° C to the maximum temperature And the speed is set at 1 占 폚 / min to 5 占 폚 / min. In the embodiment of Japanese Patent Application Laid-Open No. 2001-223104, in the composition of Sr _{1 - x} La _x (Fe _{12 - y} Co _y ) _z O ₁₉ , the heating rate is 1 ° C / min to 5 ° C / _cJ is improved. In Japanese Patent Application Laid-Open No. 2001-223104, the temperature lowering rate is not particularly limited, but is usually set at 1 ° C / minute to 20 ° C / minute. In the embodiment, the temperature lowering rate is 5 ° C / minute . In order to improve the H _cJ of the SrLaCo ferrite, the heating rate and the temperature lowering rate in the firing step are set in a specific range in addition to the above Japanese Laid-Open Patent Publication No. 2001-223104, Japanese Laid-Open Patent Publication No. 2000-277312, 2003-297623 and the like.

On the other hand, as the ferrite sintered magnet, Ca ferrite together with Sr ferrite and Ba ferrite are also known. It is known that Ca ferrite has a stable structure represented by a composition formula of CaO-Fe ₂ O ₃ or CaO-2Fe ₂ O ₃ and forms hexagonal ferrite by adding La. However, the obtained magnet characteristics are the same as those of the conventional Ba ferrite, and are not sufficiently high.

Japanese Patent No. 3181559 discloses a method of replacing a part of Ca with a rare earth element such as La in order to improve B _r and H _cJ of Ca ferrite and improve the temperature characteristics of H _cJ , (Hereinafter referred to as " CaLaCo ferrite ") having an anisotropic magnetic field H _A of 20 kOe or more, which is substituted with Sr ferrite, and the anisotropic magnetic field H _A is 10% or more higher than that of Sr ferrite.

However, although CaLaCo ferrite has an anisotropic magnetic field H _A exceeding SrLaCo ferrite, B _r and H _cJ are about the same as SrLaCo ferrite, while H _k / H _cJ is very poor, and high H _cJ and high H _k / H _cJ , so that it can not be applied to various applications such as motors.

In order to improve the magnetic properties of CaLaCo ferrite, various proposals have been made. For example, Japanese Laid-Open Patent Publication No. 2006-104050 proposes a CaLaCo ferrite in which the molar ratio and the value of n of each constituent element are optimized and La and Co are contained in a specific ratio, 060757 proposes a CaLaCo ferrite in which a part of Ca is substituted with La and Ba, and WO 2007/077811 proposes a CaLaCo ferrite in which a part of Ca is substituted with La and Sr.

However, the CaLaCo ferrite described in Japanese Laid-Open Patent Publication No. 2006-104050, International Publication No. 2007/060757 and International Publication No. 2007/077811 has improved magnet characteristics for CaLaCo ferrite proposed in Japanese Patent No. 3181559 However, it is inadequate to meet the demand for higher performance in recent years, and it is required to improve a new magnet characteristic.

International Patent Publication No. 2011/001831 discloses a CaLaCo ferrite which is proposed in Japanese Laid-Open Patent Publication No. 2006-104050, International Publication No. 2007/060757 and International Publication No. 2007/077811, wherein as a sintering aid, 1% by mass or more and, by the addition of CaCO ₃ of 1-2% by mass by mass SiO _2, and CaO in terms of less than 1.8% by mass of the calcined body, while preventing as much as possible the B _r and H _k / H _cJ of degradation, specifically the H _cJ And a CaLaCo ferrite that has been improved to a minimum.

If International Publication No. CaLaCo ferrite that includes a relatively large amount of a sintering aid is proposed in No. 2011/001831, H _cJ will exceed the increase in specific, but most of them, H _cJ is 360 kA / m (about 4.5 kOe) H _k / H _cJ is lowered to less than 85%, and therefore it is not necessarily sufficient to respond to the thinning of the ferrite sintered magnet which is recently required.

Japanese Patent Application Laid-Open No. 10-149910 Japanese Patent Laid-Open No. 11-154604 Japanese Patent Application Laid-Open No. 2001-223104 Japanese Patent Application Laid-Open No. 2000-277312 Japanese Patent Application Laid-Open No. 2003-297623 Japanese Patent No. 3181559 Japanese Patent Application Laid-Open No. 2006-104050 International Publication No. 2007/060757 International Publication No. 2007/077811 International Publication No. 2011/001831

Accordingly, an object of the present invention is to provide a method of manufacturing a ferrite sintered magnet capable of coping with thinning, in which H _cJ is improved while maintaining a high B _r and a high H _k / H _cJ , and a ferrite sintered magnet.

After a study example (銳意) in view of the above object, the inventors have found that, in the CaLaCo ferrite, as a sintering aid at the time of the addition of CaCO ₃ of not more than 2% by mass SiO _2, and CaO in terms of less than 1.8% by mass, and fired , 1100 ℃ ~ by the temperature rising rate in the sintering temperature range of the temperature lowering rate at 1 ℃ / min ~4 ℃ / minute, and the sintering temperature in a temperature range of ~1100 ℃ 6 ℃ / min or more, a high B _r and It is found that H _cJ can be improved while maintaining a high H _k / H _cJ .

Further, the inventors of the present invention have conducted a detailed analysis on the relation between the temperature rising rate and the temperature lowering rate and the structure. As a result, in CaLaCo ferrite, by firing at the above-mentioned heating rate and temperature lowering rate, The grain boundary phase is fine and the grain is scattered. When the temperature raising rate and the temperature decreasing speed are out of the above-mentioned range, the grain boundary phases existing between the three or more columnar phases are relatively large, .

That is, at the time of firing, the rate of temperature rise in the temperature range of 1100 ° C to the firing temperature is set to 1 ° C / min to 4 ° C / min, and the rate of decrease in temperature in the firing temperature to 1100 ° C is set to 6 ° C / , It is found that the intergranular phase existing between the three or more columnar phases becomes fine and scattered and thereby H _cJ is improved while maintaining a high B _r and a high H _k / H _cJ , Thereby completing the invention.

That is, the method for producing a ferrite sintered magnet of the present invention is a method for producing a ferrite sintered magnet, comprising: a step of forming a ferrite sintered magnet having a hexagonal M type magnetoplumbite structure, 1. A method for producing a ferrite sintered magnet having an existing second grain boundary phase and having an arbitrary cross section in which the second grain boundary phase is scattered and an average area of the second grain boundary phase is less than 0.2 탆 ² ,

In the general formula: Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z , which represents the atomic ratio of the metal elements of elements A, Ca, La, Ba and / or Sr,

Wherein 1-x-y, x, y and z, and n representing the molar ratio,

0.3? 1-x-y? 0.65,

0.3? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

4.5? N? 7

To prepare a raw material powder,

A calcination step of calcining the raw material powder to obtain a calcined body,

A grinding step of pulverizing the calcined body to obtain a powder,

A molding step of molding the powder to obtain a molded article, and

A sintering step of sintering the molded body to obtain a sintered body

/ RTI >

0% by mass to 1.8% by mass SiO ₂ and 0% by mass to 2% by mass CaCO ₃ in terms of CaO are added to the calcined body after 100% by mass of the calcined body after the calcining step , And

In the firing step, the temperature raising rate in the temperature range of 1100 캜 to the firing temperature is set to 1 캜 / min to 4 캜 / min, and the temperature decreasing rate in the temperature range of the firing temperature to 1100 캜 is set to 6 캜 / .

The addition amount of SiO ₂ is preferably 1% by mass to 1.8% by mass, and the amount of CaCO ₃ added is preferably 1% by mass to 2% by mass in terms of CaO.

It is preferable that the addition amount of the SiO ₂ is 1.1% by mass to 1.6% by mass, and the addition amount of CaCO ₃ is 1.2% by mass to 2% by mass in terms of CaO.

It is preferable that 900 or more of the second grain boundary phases exist within a range of 53 x 53 탆 ² of an arbitrary cross section.

The ferrite sintered magnet of the present invention is a ferrite sintered magnet having a main phase composed of ferrite having a hexagonal M type magnetoplumbite structure, a first granular phase existing between the two main phases and a second granular phase existing between the three main phases And the second granular phase is dispersed in an arbitrary cross section and the average area of the second granular phase is less than 0.2 占 퐉 ² .

The ferrite sintered magnet comprises:

Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z representing atomic ratios of metal elements of elements A, Ca, La, Ba and / or Sr, , x, y and z, and n representing the molar ratio,

0.3? 1-x-y? 0.75,

0.2? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

It is preferable to contain the element A, Ca, La, Ba and / or Sr which satisfies 3? N? 6, Fe and Co, and 0 mass% to 1.8 mass% SiO ₂ .

It is preferable that 900 or more of the second grain boundary phases exist within a range of 53 x 53 탆 ² of an arbitrary section.

According to the present invention, since H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ , it is possible to provide a ferrite sintered magnet which can sufficiently cope with thinning.

By using the ferrite sintered magnet according to the present invention, it is possible to provide various electric motors, generators, loudspeakers, and other electric parts for automobiles, electric parts, and the like that are small and light in weight and highly efficient.

BRIEF DESCRIPTION OF THE _DRAWINGS FIG. 1 is a graph showing the relationship between the rate of temperature rise and B _r and H _cJ in the sintering process of the ferrite sintered magnet of sample No. 1 of Example 1. FIG.
2 is a graph showing the relationship between the heating rate and H _k / H _cJ in the sintering process of the ferrite sintered magnet of sample No. 1 in Example 1. Fig.
3 is a graph showing the relationship between the rate of temperature rise and B _r and H _cJ in the firing step of the ferrite sintered magnet of sample No. 2 in Example 1. Fig.
4 is a graph showing the relationship between the heating rate and H _k / H _cJ in the firing step of the ferrite sintered magnet of sample No. 2 in Example 1. Fig.
5 is a graph showing the relationship between the rate of temperature decrease and B _r and H _cJ in the firing step of the ferrite sintered magnets of sample No. 3 (black circle) and 4 (black triangle) of Example 1.
6 is a graph showing the relationship between the cooling rate and H _k / H _cJ in the firing step of the ferrite sintered magnet of sample No. 3 (black circle) and 4 (black triangle) of Example 1.
7 is a graph showing the relation between the rate of temperature decrease and B _r and H _cJ in the firing step of the ferrite sintered magnets of sample No. 5 (black circle) and 6 (black triangle) of Example 1. Fig.
8 is a graph showing the relationship between the cooling rate and _Hk / _HcJ in the firing step of the ferrite sintered magnet of sample No. 5 (black circle) and 6 (black triangle) of Example 1. Fig.
9 is a photograph showing a reflected electron image of FE-SEM of a ferrite sintered magnet of sample No. 7 of Example 2. Fig.
10 is a photograph showing the reflected electron image by FE-SEM of the ferrite sintered magnet of sample No. 8 of Example 2. Fig.
11 is a photograph showing the reflected electron image of FE-SEM of the ferrite sintered magnet of sample No. 9 of Example 2. Fig.
12 is a photograph showing a reflection electron image of FE-SEM of a ferrite sintered magnet of sample No. 10 of Example 2. Fig.
13 is a photograph showing a reflection electron image of FE-SEM of the ferrite sintered magnet of sample No. 11 of Example 2. Fig.
14 is a photograph showing the reflected electron image of FE-SEM of the ferrite sintered magnet of sample No. 12 of Example 2. Fig.
15 is an image after binarization of a tissue photograph showing a reflected electron image by FE-SEM of a ferrite sintered magnet of sample No. 7 of Example 2. Fig.

[1] Manufacturing method of ferrite sintered magnet

A columnar phase composed of ferrite having a hexagonal M type magnetron plumbite structure, a first granular phase existing between the two columnar phases and a second granular phase existing between the three or more columnar phases, Wherein the second granular phase is scattered and the average area of the second granular phase is less than 0.2 占 퐉 ² is characterized in that the ferrite sintered magnet according to the present invention is a ferrite sintered magnet comprising Ca, La, Ba and / or Sr, In the general formula: Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z representing the atomic ratio of metal elements of Fe and Co,

Wherein 1-x-y, x, y and z, and n representing the molar ratio,

0.3? 1-x-y? 0.65,

0.3? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

4.5? N? 7

To prepare a raw material powder,

A calcination step of calcining the raw material powder to obtain a calcined body,

A grinding step of pulverizing the calcined body to obtain a powder,

A molding step of molding the powder and obtaining a molded body,

And a sintering step of sintering the formed body to obtain a sintered body,

0% by mass to 1.8% by mass SiO ₂ and 0% by mass to 2% by mass CaCO ₃ in terms of CaO are added to the calcined body after 100% by mass of the calcined body after the calcining step , And

In the firing step, the temperature raising rate in the temperature range of 1100 캜 to the firing temperature is set to 1 캜 / min to 4 캜 / min, and the temperature decreasing rate in the temperature range of the firing temperature to 1100 캜 is set to 6 캜 / . Each process will be described below. The ferrite sintered magnet produced by this manufacturing method will be described later.

(a) Preparation of raw material powder

Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z (where 1-xy, 1-xy, and 1-xy) represent atomic ratios of metal elements of elements A, Ca, La, Ba and / x, y and z, and n representing the molar ratio,

0.3? 1-x-y? 0.65,

0.3? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

4.5? N? 7.

And the raw material powder is prepared so as to satisfy the composition represented by the following formula.

The reasons for limiting the composition of each of the above elements will be described below. The reasons for limiting the composition range of the respective elements in a preferable composition of a ferrite sintered magnet to be described later will also be described together.

The Ca content (1-xy) is 0.3? 1-xy? 0.65. When Ca is less than 0.3, B _r and H _k / H _cJ decrease, which is not preferable. When Ca exceeds 0.65, La and A elements become relatively small and B _r and H _k / H _cJ decrease, which is not preferable. When CaCO ₃ in an amount of 2% by mass or less in terms of CaO is added to the calcined body in 100% by mass of the calcined body in the addition of a sintering auxiliary agent to be described later, the content of Ca in the calcined ferrite sintered magnet is smaller than that of the calcined body The content (1-xy) of Ca in the ferrite sintered magnet is set to 0.3 1-xy 0.75.

The content (x) of La is 0.3? X? 0.65. When La is less than 0.3 or exceeds 0.65, B _r and H _k / H _cJ decrease, which is not preferable. La may be at least one of rare earth elements other than La, and some of them may be substituted. The substitution amount is preferably in a molar ratio of 50% or less of La. When CaCO ₃ of 2% by mass or less in terms of CaO is added to the calcined body in 100% by mass of the calcined body in the addition of a sintering auxiliary agent to be described later, in the ferrite sintered magnet after calcination, The content of La is reduced accordingly. Therefore, the content (x) of La in the ferrite sintered magnet was set to 0.2? X? 0.65.

The element A is Ba and / or Sr. The content (y) of the element A is 0? Y? 0.2. The effect of the present invention is not impaired even when the A element is not contained. However, by adding the element A, crystals in the calcined body become finer and the aspect ratio becomes smaller, so that the effect of further improving H _cJ can be obtained. If the element A exceeds 0.2, SrLaCo ferrite is brought close to the grain boundary phase existing between the three or more pillar-shaped phases described later, and it is difficult to obtain a scattered structure. It is not preferable. The content of element A is relatively small in the sintered ferrite sintered magnet due to the addition of CaCO ₃ before the pulverizing step but is also the same in the sintered magnet since the amount of the element is originally small and the amount of change is small .

The content (z) of Co is 0.25? Z? 0.65. When Co is less than 0.25, improvement in magnetic characteristics due to addition of Co can not be obtained. In addition, since unreacted? -Fe ₂ O ₃ remains in the calcined body, the slurry is missing from the cavity of the mold during the wet molding. When Co exceeds 0.65, an abnormal phase containing a large amount of Co is generated and the magnetic properties are largely lowered, which is not preferable.

Co may be partially substituted with at least one selected from Zn, Ni and Mn. Particularly, by replacing a part of Co with Ni and Mn, the manufacturing cost can be reduced without lowering the magnet characteristics. Further, substituting Zn for a part of Co can improve B _r , although H _cJ is slightly lowered. The total substitution amount of Zn, Ni and Mn is preferably in a molar ratio of 50% or less of Co.

n is a value reflecting the molar ratio of (Fe + Co) and (Ca + La + A), and is represented by 2 n = (Fe + Co) / (Ca + La + A). The molar ratio n is preferably 4.5? N? 7. n is less than 4.5, as well as the quality ratio of the non-magnetic portion increases, the shape of the calcined body particles are excessively flat (扁平) is H _cJ is significantly reduced. If n is more than 7, unreacted? -Fe ₂ O ₃ remains in the calcined body and slurry is missed from the cavity of the molding die during wet molding, which is not preferable. When CaCO ₃ of 2% by mass or less in terms of CaO is added to the calcined body before the pulverization step, the content of Ca in the sintered ferrite sintered magnet is relatively larger than that of the calcined body So that n becomes smaller. Therefore, the molar ratio n of the ferrite sintered magnet was 3? N? 6.

The value of the molar ratio x / z of La and Co is preferably 1? X / z? 3. A more preferable range is 1.2? X / z? 2. By selecting a composition that satisfies the above-described values, the magnet characteristics can be further improved.

In the present invention, when the La content> the Co content> the A content, that is, x> z> y, the effect of improving the magnet characteristics is significant.

The above-mentioned composition is expressed by the atomic ratio of the metal element, but the composition containing oxygen (O)

General _{formula: Ca 1 -x- y La x A} y Fe 2n - n represents the _z Co _z O _α (However, 1-xy, x, y, z and α is molar ratio, and,

0.3? 1-x-y? 0.65,

0.3? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

4.5? N? 7

And when the stoichiometric composition ratio when La and Fe are trivalent and when Co is divalent and x = z and n = 6 are expressed,? = 19).

In the composition of the ferrite lower body containing oxygen (O), the number of moles of oxygen differs depending on the valence and n value of Fe and Co. Further, in the ferrite sintered magnet, the ratio of oxygen to the metal element changes due to vacancy of oxygen when sintered in a reducing atmosphere, change in the valence of Fe in the ferrite, change in the valence of Co, and the like. Therefore, the actual number of moles of oxygen may deviate from 19. Therefore, in the present invention, the composition is represented by the atomic ratio of the metal element that is most easily specified.

As raw material powders, oxides, carbonates, hydroxides, nitrates, chlorides and the like of the respective metals can be used regardless of the singer. Or a solution in which the raw material powder is dissolved. Examples of the Ca compound include carbonates, oxides, chlorides, and the like of Ca. Examples of the compound of La include oxides such as La ₂ O ₃ , hydroxides such as La (OH) ₃ , carbonates such as La ₂ (CO ₃ ) ₃ .8H ₂ O, and the like. As the compound of the element A, carbonates, oxides, chlorides and the like of Ba and / or Sr are exemplified. Examples of the iron compound include iron oxide, iron hydroxide, iron chloride, and a mill scale. Examples of the compound of Co include oxides such as CoO and Co ₃ O ₄ , hydroxides such as CoOOH, Co (OH) ₂ and Co ₃ O ₄ m ₁ H ₂ O (m ₁ is a positive number), carbonates such as CoCO ₃ , And basic carbonates such as m ₂ CoCO ₃ · m ₃ Co (OH) ₂ · m ₄ H ₂ O (m ₂ , m ₃ and m ₄ are positive numbers).

The raw material powders other than CaCO ₃ , Fe ₂ O ₃ and La ₂ O ₃ may be added from the time of raw material mixing, or may be added after calcination. For example, (1) CaCO ₃ , Fe ₂ O ₃ , La ₂ O _3, and Co ₃ O ₄ are mixed, and after mixing and calcining, the calcined body is pulverized, molded and sintered to produce a ferrite sintered magnet (2) mixing CaCO ₃ , Fe ₂ O ₃ and La ₂ O ₃ , mixing and calcining, adding Co ₃ O ₄ to the calcined body, pulverizing, molding and sintering to manufacture a ferrite sintered magnet You may.

In order to accelerate the reaction at the time of calcination, a compound containing B such as B ₂ O ₃ and H ₃ BO ₃ may be added to about 1% by mass as necessary. Particularly, the addition of H ₃ BO ₃ is effective for further improvement of H _cJ and B _r . The amount of H ₃ BO ₃ to be added is preferably 0.3 mass% or less, most preferably 0.2 mass% or so. When the addition amount of H ₃ BO ₃ is less than 0.1 mass%, the improvement effect of B _r is small, and when it is more than 0.3 mass%, B _r decreases. Since H ₃ BO ₃ also has the effect of controlling the shape and size of crystal grains during sintering, it may be added after calcination (before fine pulverization or before sintering) But may be added in all of the calcinations.

The mixing and mixing of the raw material powder may be performed by any of wet and dry methods. Stirring with a medium such as a steel ball can more uniformly mix the raw material powder. In the case of a wet type, it is preferable to use water as the solvent. For the purpose of enhancing the dispersibility of the raw material powder, known dispersants such as ammonium polycarboxylate and calcium gluconate may be used. The mixed raw slurry is dewatered to a mixed raw material powder.

(b) Calcination process

The raw material powder after mixing is solid-phase-reacted by heating using an electric furnace or a gas furnace to form a ferrite compound having a hexagonal M type magnetoplumbite structure. This process is referred to as " calcination ", and the obtained compound is referred to as " calcined body ".

The calcination step is preferably carried out in an atmosphere having an oxygen concentration of 5% or more. If the oxygen concentration is less than 5%, abnormal lip growth and abnormal phase generation are caused. A more preferable oxygen concentration is 20% or more.

In the calcination step, the solid phase reaction in which the ferrite phase is formed progresses with increasing temperature and is completed at about 1100 ° C. If the calcination temperature is lower than 1100 ° C, unreacted hematite (iron oxide) remains, and the magnet characteristics are lowered. On the other hand, when the calcination temperature exceeds 1450 DEG C, the crystal grains grow excessively, so that it may take a long time to grind in the grinding step. Therefore, the calcination temperature is preferably 1100 ° C to 1450 ° C, and more preferably 1200 ° C to 1350 ° C. The calcination time is preferably 0.5 to 5 hours.

When H ₃ BO ₃ is added before the calcination, the ferrite reaction is promoted, so that calcination can be performed at 1100 ° C. to 1300 ° C.

(c) Addition of sintering aid

As the sintering auxiliary, after calcining step, before the forming step to be described later, 0% by mass to 1.8% by mass of SiO ₂ with respect to 100% by mass of the calcined body and 0% by mass of CaO with respect to 100% It is preferable to add CaCO ₃ in an amount of 2% by mass to 2% by mass. The method of adding the sintering aid may be a method of adding a sintering auxiliary agent to a calcined body obtained by the calcining step and then carrying out a pulverization step, a method of adding a sintering auxiliary agent during the pulverization step, a method of adding a sintering auxiliary agent to the calcined body, A method of performing a molding process after mixing, and the like.

When the addition amount of SiO ₂ exceeds 1.8 mass%, H _cJ decreases and B _r and H _k / H _cJ also decrease, which is not preferable. In order to further improve H _cJ , a more preferable addition amount is 1% by mass to 1.8% by mass, and a most preferable addition amount is 1.1% by mass to 1.6% by mass. It is most preferable to add SiO ₂ to the calcined body, but a part of the total added amount may be added before calcination (when the raw powder is mixed). By adding it before calcination, the size of the crystal grains at calcination can be controlled.

CaCO ₃ is added in an amount of 2 mass% or less in terms of CaO based on 100 mass% of the calcined body. Addition of CaCO ₃ can improve H _cJ . When the addition amount of CaCO ₃ exceeds 2 mass%, B _r and H _k / H _cJ decrease, which is not preferable. The preferred amount of the body is 1% by mass to 2% by mass, more preferably 1.2% by mass to 2% by mass. With such a preferred addition amount, extremely high H _cJ exceeding 500 kA / m (about 6.3 kOe) can be expressed. In the present invention, the addition amount of CaCO ₃ is expressed in terms of CaO. The addition amount of CaCO ₃ from the added amount in terms of CaO,

(Molecular weight of CaCO ₃ x addition amount in terms of CaO) / molecular weight of CaO

. ≪ / RTI >

For example, when 1.5 mass% of CaCO ₃ is added in terms of CaO,

{(40.08 [atomic weight of Ca] + 12.01 [atomic weight of C] + 48.00 [O atomic weight × 3 in] = 100.09 [molecular weight of CaCO _3]) × 1.5% by weight [amount in terms of CaO]} / (40.08 [Ca ] + 16.00 [atomic weight of O] = 56.08 [molecular weight of CaO]) = 2.677 mass% [amount of addition of CaCo ₃ ].

It is possible to further improve the magnetic characteristics by setting the ratio of CaCO ₃ to SiO ₂ [amount of CaCO ₃ (in terms of CaO) / amount of SiO ₂ added] to 0.8 to ₂ .

Since CaLaCo ferrite according to the present invention contains Ca as a columnar component, a liquid phase can be produced and sintered without adding SiO ₂ and CaCO ₃ as sintering aids. That is, in the ferrite sintered magnet, the intergranular phase is formed without adding the above-mentioned SiO ₂ and CaCO ₃ mainly forming the intergranular phase. It is possible to carry out the present invention without adding SiO ₂ and CaCO _3. However, if these compounds are not added, it is possible to obtain a structure in which the intergranular phase existing between the three or more pillar phases described below is fine, And H _cJ may be lowered. Therefore, it is preferable to add the above SiO ₂ and / or CaCO ₃ in order to prevent the decrease of H _cJ .

In addition to the above-mentioned SiO ₂ and CaCO ₃ , Cr ₂ O ₃ , Al ₂ O ₃ and the like may be added after the calcining step and before the forming step described later to improve the magnet characteristics. The addition amount thereof is preferably 5% by mass or less.

(d) milling process

The calcined body is pulverized by a vibrating mill, a ball mill, an attritor, or the like to obtain a pulverized powder. The average particle size of the pulverized powder is preferably about 0.4 mu m to 0.8 mu m (air permeation method). The pulverizing step can be carried out both by dry pulverization and wet pulverization, but it is preferable to carry out both of them in combination.

The wet pulverization is carried out using water and / or a non-aqueous solvent (organic solvent such as acetone, ethanol, xylene). By wet pulverization, a slurry in which water (solvent) and calcined body are mixed is produced. It is preferable that a known dispersant and / or a surfactant is added to the slurry in an amount of 0.2% by mass to 2% by mass in terms of solid content. After the wet grinding, it is preferable to concentrate and knead the slurry.

The pulverized powder contains ultrafine powder of less than 0.1 占 퐉 which causes dehydration and malformation, and it is preferable to perform the heat treatment on the pulverized powder in order to remove these ultrafine powder. The powder subjected to the heat treatment is preferably pulverized again. As described above, it is possible to carry out the pulverization step (the pulverization step) comprising the first pulverization step, the step of heat-treating the powder obtained by the first pulverization step, and the second pulverization step of pulverizing the powder subjected to the heat treatment Hereinafter referred to as " heat treatment re-pulverization step "), H _cJ can be improved.

In the conventional pulverizing step, a superfine particle of less than 0.1 탆 inevitably occurs. _HcJ decreases due to the presence of the ultrafine powder, and the dewatering property in the forming process deteriorates, resulting in defects in the molded body, The press cycle is lowered. When the powder containing the ultrafine powder obtained by the first pulverization step is subjected to the heat treatment, a reaction occurs between the powder having a relatively large particle diameter and the ultrafine powder, and the amount of ultrafine powder can be reduced. Then, particle size adjustment and necking are removed by a second milling process to produce a powder having a predetermined particle size. This makes it possible to obtain a powder having a small amount of ultrafine powder and an excellent particle size distribution, to improve H _cJ, and to solve the above-mentioned problems in the molding process.

Using the improvement effect of H _cJ by the heat treatment re-pulverizing step, even if the particle size of the powder by the second pulverization step is set relatively large (for example, about 0.8 μm to 1.0 μm (air permeation method) It is possible to obtain H _cJ equivalent to that obtained by using a powder obtained by an ordinary pulverizing process (on the order of an average particle size of about 0.4 μm to 0.8 μm (air permeation method)). Therefore, the time of the second pulverization step can be shortened, and the dewaterability can further be improved and the press cycle can be improved.

As described above, according to the heat treatment material grinding step, various advantages can be obtained, but an increase in cost due to an increase in the manufacturing process can not be avoided. However, the effect of improving the magnet characteristics obtained when the heat treatment re-pulverization step is employed is much larger than that in the case of producing the conventional ferrite sintered magnet, so that the cost increase can be offset. Therefore, in the present invention, the heat treatment material pulverizing step is a process having a practical value.

The first pulverization is carried out using a vibrating mill, a jet mill, a ball mill, an atritor, or the like as in the case of the above-mentioned conventional pulverization. The average particle size of the powder after the pulverization is preferably about 0.4 to 0.8 mu m (air permeation method). The pulverizing step can be carried out both by dry pulverization and wet pulverization, but it is preferable to carry out both of them in combination.

The heat treatment to be performed after the first pulverization step is preferably performed at 600 ° C to 1200 ° C, more preferably 800 ° C to 1100 ° C. The time for the heat treatment is not particularly limited, but is preferably 1 second to 100 hours, more preferably 1 hour to 10 hours.

The second pulverization to be performed after the heat treatment step is carried out using a vibration mill, a jet mill, a ball mill, an atritor, and the like as in the case of the first pulverization. Since the desired particle size has already been obtained in the first pulverization step, the particle size adjustment and the necking are mainly removed in the second pulverization step. Therefore, it is preferable to reduce the pulverization conditions by shortening the pulverization time or the like, rather than the first pulverization step. When pulverization is carried out under the same conditions as in the first pulverization step, superfine particles are regenerated, which is undesirable.

When it is desired to obtain a higher H _cJ than the ferrite sintered magnet obtained by the ordinary milling step, the average grain size of the powder after the second milling is set to about 0.4 μm to 0.8 μm (air permeation method) similarly to the ordinary milling step When it is desirable to utilize the advantages of shortening the time of the pulverizing process, further improving the dewatering property, and improving the press cycle, the pressure is preferably 0.8 to 1.2 mu m, preferably 0.8 to 1.0 mu m ).

(e) Molding process

The slurry after the pulverization is press-molded in a magnetic field or in a non-magnetic system while removing water (solvent). By press forming in the magnetic field, the crystal orientation of the powder particles can be aligned (oriented), and the magnet characteristics can be dramatically improved. In order to improve the orientation, 0.01% by mass to 1% by mass of a dispersant and a lubricant may be added, respectively. It is also possible to concentrate the slurry as required before molding. Concentration is preferably performed by centrifugation, filter press, or the like.

(f) Firing process

The formed body obtained by press molding is degreased and sintered (sintered) if necessary. Thus, a sintered body (sintered magnet) is obtained. It is preferable that the rate of temperature rise in the temperature range of 1100 캜 to the firing temperature is 1 캜 / min to 4 캜 / min and the rate of temperature decrease in the temperature range of the firing temperature to 1100 캜 is 6 캜 / min or more Which is characteristic of the production method of the present invention.

In the firing step, the rate of temperature rise in the temperature range of 1100 占 폚 to the firing temperature is set to 1 占 폚 / min to 4 占 폚 / min, and the rate of temperature decrease in the temperature range of firing temperature to 1100 占 폚 is 6 占 폚 / A ferrite sintered magnet having a main phase composed of ferrite having a hexagonal M type magnetron plumbite structure, a first granular phase existing between two columnar phases and a second granular phase existing between three or more main phases, in any cross-section, and the second grain boundary phase is dispersed, and further the average area of the second grain boundary phase becomes less than ² 0.2㎛ tissue, whereby, while maintaining a high B _r and high H _k / H _cJ H _cJ can be improved and a ferrite sintered magnet capable of coping with thinning can be manufactured.

It is possible to improve H _cJ while maintaining a high B _r and a high H _k / H _cJ even at a heating rate of less than 1 ° C / min, for example, at a rate of 0.5 ° C / min. However, if the heating rate is too slow, The cycle is not only long but also leads to an increase in production cost. On the other hand, when the heating rate exceeds 4 ℃ / min, in any cross section of the ferrite sintered magnet, wherein the tissue to a second grain boundary is unevenly distributed, or the average area of the second grain boundary phase is at least ² H 0.2㎛ _cJ is lowered. Therefore, the temperature raising rate is preferably 1 占 폚 / min to 4 占 폚 / min. More preferably, the temperature raising rate is 1 占 폚 / min to 2 占 폚 / min.

The rate of decline is, 6 ℃ / minute or less, in any cross section of the ferrite sintered magnet, the second tissue to the grain boundary phase is unevenly distributed or wherein an average area of at least 2 of the grain boundary phase ² 0.2㎛ doeah H _cJ is Which is undesirable. On the other hand, if the temperature is higher than 6 ° C / min, the H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ , so that if the cooling rate is excessively high, cracks may occur in the sintered body . Further, in order to rapidly lower the temperature, a cooling device or a blowing device is required in the firing furnace, which may increase the production cost. Taking this into consideration, the upper limit of the temperature lowering speed is preferably about 10 캜 / minute.

The temperature range in which the temperature raising rate is 1 deg. C / min to 4 deg. C / min is 1100 deg. C to the firing temperature. If the heating rate is temporarily higher than 4 ° C / min in a temperature range of 1100 ° C or more, there is a possibility that the second granular phase is dispersed and a structure having an average area of the second granular phase of less than 0.2 탆 ² can not be obtained , And H _cJ may be lowered. If the heating rate in the temperature range of 1100 캜 to the firing temperature is 1 캜 / min to 4 캜 / min, the rate of temperature rise at other temperatures is not particularly limited.

The temperature range in which the cooling rate is 6 ° C / min or more is the firing temperature to 1100 ° C. Is less than 1100 ℃ temperature range eurorado temperature lowering rate is temporarily 6 ℃ / min or more in the second grain boundary phase is dispersed, and is also likely to mean the area of the second grain boundary phase be less than the tissue can not be obtained 0.2㎛ ² And H _cJ may be lowered. If the rate of temperature reduction in the temperature range from the firing temperature to 1100 占 폚 is 6 占 폚 / min or more, the rate of temperature decrease at other temperatures is not particularly limited.

The firing is carried out using an electric furnace, a gas furnace, or the like. The firing is preferably performed in an atmosphere having an oxygen concentration of 10% or more. If the oxygen concentration is less than 10%, abnormal grain growth, generation of abnormal phase, and the like are caused and the magnet characteristics are deteriorated. The oxygen concentration is more preferably 20% or more, and most preferably 100%. The firing temperature is preferably 1150 ° C to 1250 ° C. The firing time is preferably 0.5 to 2 hours. The average crystal grain size of the sintered magnet obtained by the sintering process is about 0.5 to 2 mu m.

After the sintering process, a ferrite sintered magnet is finally produced through a known manufacturing process such as a machining process, a cleaning process, and an inspection process.

As described above, the feature of the present invention resides in that the rate of temperature rise from 1100 deg. C to the firing temperature is decreased (1 deg. C / min to 4 deg. C / min) and the firing temperature after firing is changed to 1100 deg. (6 DEG C / min or more) faster than the rate of temperature rise. Thus, H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ . The reason why the inventors estimate them will be described below. However, this reason is estimated from the knowledge obtained at present, and is not intended to limit the technical scope of the present invention.

The sintering process of a conventional ferrite sintered magnet including the ferrite sintered magnet according to the present invention is classified into liquid phase sintering. In the present invention, when SiO ₂ and CaCO ₃ are added as sintering aids, the sintering auxiliary becomes a part of the liquid phase component. When the sintering aids are not added, Ca contained as the main phase component becomes a part of the liquid phase component . After sintering, these liquid phases become a first grain boundary phase existing between two columnar phases and a second grain boundary phase existing between three or more columnar phases.

In the present invention, dissolution and precipitation into a solid phase liquid phase can be promoted by slowly passing the temperature region at a heating rate of 1 ° C / minute to 4 ° C / minute in a temperature range of 1100 ° C to a firing temperature , Resulting in formation of a structure in which the optimum structure, that is, the second grain boundary phase is dispersed, and the average area thereof is less than 0.2 탆 ² .

However, when the temperature is lowered from 1100 占 폚 to the sintering temperature at the time of lowering the temperature after the sintering, dissolution and precipitation into the solid phase are caused again, and the optimized structure is destroyed. Thus, by making the cooling rate at 6 ° C / min or more in the temperature range of the firing temperature to 1100 ° C and passing the temperature region quickly, it is possible to maintain the structure in which the second grain boundary phase is scattered and the average area is less than 0.2 μm ² And as a result, it is believed that H _cJ can be improved while maintaining high B _r and high H _k / H _cJ .

It is considered that the dissolution and precipitation into the solid phase in the firing process occur not only in the CaLaCo ferrite of the present invention but also in the SrLaCo ferrite. However, CaLaCo ferrite and SrLaCo ferrite differ greatly in the following respects.

In the CaLaCo ferrite, when SiO ₂ and CaCO ₃ are added as sintering aids as described above, the sintering auxiliary agent forms a liquid phase at the time of sintering, and when the sintering auxiliary agent is not added, Ca becomes a part of the liquid phase component. That is, Ca is contained in both the main phase and the liquid phase. In the firing step, it is considered that Ca contained in the main phase and Ca contained in the liquid phase move with each other when dissolution and precipitation into the above-mentioned solid phase liquid occurs. That is, dissolution and precipitation into a solid phase liquid phase are promoted by the mutual movement of Ca between the main phase and the liquid phase, and as a result, a structure in which the second phase boundary phase is dispersed and the average area is less than 0.2 탆 ² is formed It is considered.

On the other hand, SrLaCo ferrite basically does not contain Ca in the main phase. Therefore, at the time of sintering, SiO ₂ or CaCO ₃ added as a sintering aid mainly forms a liquid phase. Inventors, SrLaCo ferrite sintered _magnet-in (Sr _{1 x} La _x Fe _y Co _{y .6- 11,} the addition of CaCO ₃ 1.5% by mass to 1.2% by mass of SiO ₂ and CaO in terms of a sintering aid), and any The composition of the three intergranular phases was subjected to point analysis by FE-TEM equipped with a scanning transmission electron microscope (STEM) and an energy dispersive X-ray spectroscopy (EDS) function, and the results shown in Table 1 were obtained. The unit of the content is all atomic%.

[Table 1]

As shown in Table 1, Sr, La, and Fe were included in the grain boundary phase of SrLaCo ferrite sintered magnet in addition to Si and Ca added as sintering aids. According to these results, it is considered that, in the SrLaCo ferrite, when the above-mentioned solid phase dissolution and precipitation occurs in the liquid phase, the main phase is dissolved and the main phase phase component moves to the liquid phase.

It is known that the stability of the ferrite phase having a hexagonal M type magnetron plumbite structure is Sr ferrite> SrLaCo ferrite> CaLaCo ferrite. As described above, Ca in the main phase and Ca contained in the liquid in the CaLaCo ferrite are considered to be shifted from each other because the ferrite phase of CaLaCo ferrite is unstable compared with Sr ferrite or SrLaCo ferrite . Therefore, in the SrLaCo ferrite in which the ferrite phase is stable, it is considered that the liquid phase component does not migrate to the main phase even if the main phase is dissolved and the main phase component moves to the liquid phase. That is, it is considered that the stable SrLaCo ferrite phase can not become unstable including Ca. Therefore, in the case of SrLaCo ferrite, there is no mutual movement between the main phase and the liquid phase when dissolution and precipitation into the solid phase are caused, and Sr or La of the main phase phase is considered to be unilaterally moving in the liquid phase. Sr or La of the columnar component dissolves in the liquid phase, that is, Sr or La elutes from the R block layer of the outer shell of the columnar body, and only the spinel block layer remains, and the crystal magnetic anisotropy near the columnar interface is lowered And the H _cJ of the sintered magnet is lowered. In addition, when the main phase is dissolved, the main phase ratio in the entire sintered magnet is lowered, which is considered to be a factor of lowering B _r .

As shown in the examples described later, also in the ferrite sintered magnet according to the present invention, the columnar component moves in the granular phase (liquid phase). However, as described above, in the CaLaCo ferrite, and the Ca is contained in both of the main phase and the liquid phase, since the dissolution and precipitation of the solid phase the liquid phase promotes according to the Ca mutual movement between the main phase and the liquid phase, H _cJ and B _It is believed that the H _cJ can be improved while keeping the high B _r and the high H _k / H _cJ optimized without tissue degradation.

As described above, it is believed that CaLaCo ferrite and SrLaCo ferrite have different phenomena when dissolution and precipitation into solid phase liquid occurs. Therefore, in the SrLaCo ferrite, as in the present invention, it is considered that the second granular phase is scattered on an arbitrary cross section, and a structure in which the average area of the second granular phase is less than 0.2 탆 ² is not formed. It is believed that the structure is characteristic of CaLaCo ferrite or appears remarkably in CaLaCo ferrite.

The reason why different phenomena appear is revealed by the description of prior art documents in which the rate of temperature rise and the rate of temperature decrease in SrLaCo ferrite are specified.

Japanese Patent Application Laid-Open No. 2001-223104 discloses a method in which the temperature raising rate is set at 1 占 폚 / min to 5 占 폚 / min (the temperature decreasing rate is 1 占 폚 / min to 20 占 폚 / min in the specification, H _cJ is improved. As described above, when only the temperature raising rate to 1 ℃ / min ~5 ℃ / min do not need to control the rate of temperature reduction phenomenon that H _cJ is improved itself, it is CaLaCo ferrite and is different. Japanese Patent Application Laid-Open No. 2001-223104 discloses that a part of the starting material is added even after the calcination (so-called " post-addition ") and the improvement effect of H _cJ is attributable to the heating rate alone, I'm not sure.

Further, in Japanese Unexamined Patent Publication No. 2000-277312, it is described that the H _cJ is improved by setting both the temperature raising rate and the temperature lowering rate at 900 占 폚 or higher and 1 占 폚 / min to 4 占 폚 / min. And a 1 ℃ / min ~4 ℃ / min all of the heating rate and the temperature decrease rate, that is, both the phenomenon of self-late H _cJ is improved by, it is CaLaCo ferrite and is different. In this document, Al ₂ O ₃ is indispensably contained, and it is not clear whether the improvement effect of H _cJ is due to the temperature increase, the temperature decrease rate or the content of Al ₂ O ₃ .

Further, in Japanese Laid-Open Patent Application No. 2003-297623, it is described that, in SrLaCo ferrite, H _cJ is improved when the rate of decrease in temperature during firing is set to 5 ° C / min or more, but the rate of temperature rise is not specified The rate of temperature rise is 5 deg. C / minute). As described above, the phenomenon in which H _cJ is improved when the cooling rate is set to 5 ° C / min or more is also different from CaLaCo ferrite.

[2] ferrite sintered magnets

The ferrite sintered magnet of the present invention is a ferrite sintered magnet having a main phase composed of ferrite having a hexagonal M type magnetoplumbite structure, a first granular phase existing between the two main phases and a second granular phase existing between the three main phases And the second granular phase is dispersed in an arbitrary cross section and the average area of the second granular phase is less than 0.2 占 퐉 ² .

The main phase constituting the ferrite sintered magnet of the present invention is a ferrite phase having a hexagonal M type magnetoplumbite structure. Generally, a magnetic material, particularly a sintered magnet, is composed of a plurality of compounds, and a compound that determines the properties (physical properties, magnetic characteristics, etc.) of the magnetic material is defined as " columnar phase ". The ferrite phase having the columnar phase of the present invention, that is, the hexagonal M type magnetopulmate structure also determines the basic part such as the physical properties and the magnetic characteristics of the ferrite sintered magnet of the present invention.

Means that the X-ray diffraction pattern of the hexagonal M-type magnetoplumbite structure is mainly observed when the X-ray diffraction of the ferrite sintered magnet is measured under ordinary conditions .

The ferrite sintered magnet of the present invention contains, in addition to the main phase, a first granular phase existing between two columnar phases and a second granular phase existing between three or more columnar phases. The first grain boundary phase present between the two columnar phases is an intergranular phase also known to those skilled in the art as " two grain grain boundary phase ". When the ferrite sintered magnet is observed at an arbitrary cross section, It refers to a line-shaped grain boundary. The second grain boundary phase existing between the three or more columnar phases is an intergranular phase referred to as " triple point grain boundary phase " or the like in the art, and when an arbitrary cross section of the ferrite sintered magnet is observed, A substantially triangular shape, a substantially polygonal shape, or an amorphous shape, which are present between the inner surface and the outer surface. Since the first granular phase is very thin and difficult to observe in an X-ray diffraction pattern, it is preferable to confirm it with a transmission electron microscope having high resolution. In the following description, when the first grain boundary phase and the second grain boundary phase are expressed in a combined manner, they may be simply referred to as " grain boundary phase ".

The second grain boundary phase has a sparse structure in an arbitrary section of the ferrite sintered magnet. In other words, it is a structure that exists scattered around an arbitrary section. The second grain boundary phases are connected to each other, or the crystal grain is biased to a specific region. When the second grain boundary phase becomes a ubiquitous structure, H _cJ is lowered.

In the ferrite sintered magnet of the present invention in the second grain boundary phase, the average area of each grain boundary phase is less than 0.2 mu m < ^{2 &} gt ;. As shown in the following examples, when the average area is 0.2 m ² or more, H _cJ is lowered. The average area of the second grain boundary phase is obtained by binarizing the image of the reflected electron image (BSE phase) of the end face of the ferrite sintered magnet by FE-SEM (field emission scanning electron microscope) to calculate the area and number of the second grain boundary phase And the total area is divided by the number. For example, in the case where the second grain boundary phase is ubiquitous, the average area may be less than 0.2 탆 ^{2 in the} area where the second grain boundary phase is small. In such a case, it is preferable to obtain an average area at a plurality of locations on different arbitrary sections and obtain an average value thereof.

As described above, the average area of the fine second grain boundary phase of less than 0.2 탆 ² is dispersed, so that H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ .

In a preferred embodiment, the second grain boundary phase is a structure in which 900 or more exist within a range of 53 x 53 탆 ² of an arbitrary section. When the number of the second grain boundary phase is less than 900, there is a high possibility that the average area becomes 0.2 탆 ² or more.

As described above, since the ferrite sintered magnet according to the present invention contains Ca as a columnar component, a liquid phase can be generated and sintered without adding SiO ₂ and CaCO ₃ as sintering aids. In this case, the intergranular phase to be formed mainly contains Ca. On the other hand, when 1.8% by mass or less of SiO ₂ and 100% by mass or less of CaCO ₃ in terms of CaO are added to the calcined body, these SiO ₂ and CaCO ₃ mainly form an intergranular phase . Therefore, Si and Ca are necessarily included in the grain boundary phase.

The ferrite sintered magnet of the present invention may have, in addition to the columnar phase and grain boundary phase, a third phase having a higher atomic ratio of La than the columnar phase. The third phase means "third phase" when the main phase is the first phase and the intergranular phase is the second phase, and does not define the composition ratio or the deposition order. The third phase is not essential in the present invention, and the constitution and effect of the present invention are not impaired by the presence or absence of the third phase. The ferrite sintered magnet of the present invention permits the presence of an abnormal phase (spinel phase or the like) or an impurity phase observed by X-ray diffraction or the like in a very small amount (about 5 mass% or less). For the above quantitative determination from the X-ray diffraction, the same method as the Rietveld analysis can be used.

The ferrite sintered magnet according to the present invention is a ferrite sintered magnet according to the present invention, which is represented by the general formula: Ca _{1 -x- y} La _x A _y Fe _{2n - z,} which represents the atomic ratio of metal elements of elements A, In Co _z , 1-xy, x, y and z, and n representing the mole ratio,

0.3? 1-x-y? 0.75,

0.2? X? 0.65,

0? Y? 0.2,

0.25? Z? 0.65, and

It is preferable to contain the element A, Ca, La, Ba and / or Sr which satisfies 3? N? 6, Fe and Co, and 0 mass% to 1.8 mass% SiO ₂ . When each element is out of the above-mentioned composition range, at least one of B _r , H _cJ and H _k / H _cJ decreases, which is not preferable. The reason for limiting the composition range of each element is as described above.

[Example]

The present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example 1

The composition formula _{Ca 1 -x- y La x A y} Fe 2n - in _{z Co z, x = 0.5,} y = 0, z = 0.3 and n = CaCO ₃ powder so that the 5.2, La (OH) ₃ powder, Fe ₂ O ₃ powder and Co ₃ O ₄ powder were prepared, mixed with a wet ball mill for 4 hours, and then dried and sized. Subsequently, the resultant was calcined in the air at 1300 DEG C for 3 hours, and the obtained calcined body was coarsely pulverized by a hammer mill to obtain coarse pulverized powder.

0.6% by mass of SiO ₂ and 0.7% by mass of CaCO ₃ in terms of CaO were added to 100% by mass of the crude pulverized powder, and an average particle size of 0.55 μm was measured by an air permeation method using water as a solvent Lt; / RTI > While removing the solvent, the obtained fine pulverized slurry was molded at a pressure of about 50 MPa while applying a magnetic field of about 1.3 T so that the direction of the pressure and the direction of the magnetic field were parallel to each other to form a plurality of columnar formed bodies A ).

A molded product B was obtained in the same manner as in the case of the molded product A except that the addition amount of SiO ₂ was changed to 1.2% by mass and the added amount of CaCO ₃ was changed to 1.5% by mass in terms of CaO with respect to 100% by mass of the coarse ground powder.

The obtained molded bodies A and B were charged into a firing furnace and fired at a heating rate and a firing rate shown in Table 2 to obtain ferrite sintered magnets (Samples Nos. 1 to 6). The rate of temperature rise and the rate of temperature decrease shown in Table 2 indicate the rate of temperature rise from 1100 ° C to 1210 ° C (firing temperature) and the rate of temperature decrease from 1210 ° C (firing temperature) to 1100 ° C, respectively. Samples No. 1 and 2 , Samples No. 3 to 6 were sintered in combination of a temperature raising rate of 8, a temperature of 6, and a temperature of 8, of 0.1, 0.5, 1, 2, 3, 4 or 5 or 6.67 ° C / A heating rate of 2 ° C / min and a temperature decreasing condition of 1, 4, 5, 7 and 10 were combined and sintering was carried out by holding at 1,210 ° C (sintering temperature) for 1 hour. Further, the temperature was elevated from room temperature to 1100 占 폚 at 7.5 占 폚 / min, and cooling from 1100 占 폚 to room temperature was performed by turning off the power of the baking furnace and opening the furnace door.

[Table 2]

The measurement results of B _r and H _cJ of the ferrite sintered magnet of sample No. 1 are shown in Fig. 1, and the measurement results of H _k / H _cJ are shown in Fig. The measurement results of B _r and H _cJ of the ferrite sintered magnet of sample No. 2 are shown in Fig. 3, and the measurement results of H _k / H _cJ are shown in Fig. In Figs. 1 and 3, the plot of the black circle represents the value of B _r , and the plot of the black triangle represents the value of H _cJ . In H _k / H _cJ , H _k is a value of H at a position where J is a value of 0.95B _r at the second upper limit of J (magnitude of magnetization) - H (intensity of magnetic field) curve Hereinafter the same).

The measurement results of B _r and H _cJ of the ferrite sintered magnets of sample No. 3 and sample No. 4 are shown in Fig. 5, and the measurement results of H _k / H _cJ are shown in Fig. The measurement results of B _r and H _cJ of the ferrite sintered magnets of sample No. 5 and sample No. 6 are shown in Fig. 7, and the measurement results of H _k / H _cJ are shown in Fig. 5 and 7, the solid line represents the value of B _r , and the dotted line represents the value of H _cJ . 5 and 6, plots of black circles represent samples No. 3, plots of black triangles represent sample No. 4, and plots of black circles represent samples No. 5, A plot of the black triangle shows Sample No. 6.

1 and the, SiO ₂ and CaCO ₃ samples No.1 was a temperature raising rate of addition of the 0.7 mass% in terms of CaO and 0.6% by weight as indicated in Figure 2 by 1 ℃ / min ~4 ℃ / minute in the , B _r and H _k / H _cJ slightly decreased, but H _cJ was remarkably improved and H _k / H _cJ was maintained at 85% or more.

As shown in Fig. 3 and Fig. 4, Sample No. _{2 in which} 1.2 mass% of SiO ₂ and 1.5 mass% of CaCO ₃ in terms of CaO were added was heated at a rate of 1 ° C / min to 4 ° C / min , The degradation of B _r is hardly visible, H _cJ is significantly improved, and extremely high values up to now exceeding 500 kA / m (about 6.3 kOe) were obtained. H _k / H _cJ was slightly lower than 85%, but maintained a high value.

5 and 6, the SiO ₂ and CaO in terms of 0.6% by mass of CaCO ₃ was added 0.7% by weight and the heating rate 1 ℃ / min Sample No.3 and temperature rising rate is 4 ℃ / min sample In No. 4, the B _r was slightly improved and the H _cJ was remarkably improved in the samples No. 3 and 4 when the cooling rate was 6 ° C / min or more. In addition, H _k / H _cJ maintained more than 85%. B _r and H _k / H _cJ were slightly higher overall in Sample No. 3 at a heating rate of 1 ° C / min.

7 and 8, 1.5 mass% of CaCO ₃ in terms of 1.2 mass% of SiO ₂ and CaO was added, and a sample No. 5 having a temperature raising rate of 1 캜 / minute and a sample having a temperature raising rate of 4 캜 / In No. 6, when the rate of temperature decrease was 6 ° C / min or more, no decrease in B _r was observed in all of samples No. 5 and 6, H _cJ was remarkably improved, and 500 kA / m kOe), which is an extremely high value, has been obtained. The decrease in H _k / H _cJ was hardly observed, but the sample No. 5 at a heating rate of 1 ° C / minute was slightly higher overall and maintained at 85% or more. Sample No. 6 with a heating rate of 4 캜 / min was slightly lower than 85%, but maintained a high value.

As described above, according to the ferrite sintered magnet manufacturing method of the present invention, since H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ , it is possible to provide a ferrite sintered magnet capable of sufficiently coping with thinning . Further, according to a preferred embodiment, an extremely high H _cJ of not more than 500 kA / m (about 6.3 kOe) can be obtained while maintaining a high H _k / H _cJ of 85% or more.

Example 2

Ferrite sintered magnets of sample Nos. 7 to 12 were obtained in the same manner as in Example 1, except that the addition amount of SiO _{2, the} addition amount of CaCO ₃ (CaO conversion value), the heating rate and the cooling rate shown in Table 3 were used. Sample No. 7 is a ferrite sintered magnet identical to that of Sample No. 1 of Example 1 at a temperature raising rate of 1 캜 / minute, and Sample No. 8 is a sample of Sample No. 2 of Example 1, ° C / minute, and Sample No. 9 is a ferrite sintered magnet identical to that of Sample No. 3 of Example 1 at a temperature decreasing rate of 1 ° C / minute, Sample No. 10 is a ferrite sintered magnet identical to Sample No. 10 of Example 1 .5 is a ferrite sintered magnet the same as that in which the temperature decreasing rate is 1 占 폚 / min.

[Table 3]

Observation of the structure of the obtained cylindrical sintered magnet was performed by a reflection electron image (BSE phase) using FE-SEM (field emission scanning electron microscope). Tissue observation was performed on a plane perpendicular to the axial direction of the cylindrical sintered magnet (c-plane), and three tissue photographs were taken at an arbitrary cross section. The results are shown in Figs. 9 to 14. Figs. 9 to 14 show the photographs of the samples Nos. 7 to 12, respectively. The photographs at the top, middle, and bottom in each figure are the photographs of three fields of view taken at arbitrary cross sections, The left side of the drawing is taken at a magnification of 2000 times and the right side is photographed at a magnification of 5000 times.

In Figs. 9 to 12, the black part in the figure is a second grain boundary phase existing between three or more pillar-shaped phases, and the grayish gray, gray, and white gray are all the main phases. In the photograph of the tissue on the right side of each of the drawings, what appears linear in the grain boundaries of the main phase and the main phase is the first grain boundary phase existing between the two main phases.

9 and 10, the ferrite sintered magnet of the present invention has a first grain boundary phase existing between a main phase and two main phase phases and a second grain boundary phase existing between three or more main phases , And the second grain boundary was fine and scattered. On the other hand, as can be seen from Figs. 11 to 14, the ferrite sintered magnet of the comparative example contains the second granular phase unevenly and the second granular phase which is remarkably large.

A binarization process is performed on an arbitrary 53 × 53 袖 m ² range of the left side tissue photograph (magnification 2000 times) in Figs. 9 to 14, the second grain boundary phase is removed from the background image, And the average area (area / number) was calculated from the total area and the number. Further, the total area, the number, and the average value of the average area (average value of three fields of view) of each of the three fields of view in each drawing were obtained. The results are shown in Table 4. An example of an image after binarization processing of a tissue photograph (magnification 2000 times) on the upper left side in Fig. 9 is shown in Fig. In Fig. 15, the second grain boundary phase is displayed to be white by image processing. By image analysis of this image, the area and the number of the white portion (second intergranular phase) on the image were obtained.

[Table 4]

As can be seen from Table 4, the average area of the second grain boundary phase in the ferrite sintered magnet of the present invention was all less than 0.2 탆 ² , and the average value of the three fields in each of the drawings was also less than 0.2 탆 ² . On the other hand, the average area of the second grain boundary phase in the ferrite sintered magnet of the comparative example may be partially less than 0.2 mu m < ^{2 &} gt ;, but the average value of the three fields is not less than 0.2 mu m ² , .

Further, the number of the second grain boundary phases in the ferrite sintered magnet of the present invention was 900 or more in all, whereas the number of the second grain boundary phases in the ferrite sintered magnet of the comparative example was less than 900.

As described above, in the ferrite sintered magnet of the present invention, in the sintering step, the temperature raising rate in the temperature range of 1100 캜 to the sintering temperature is set to 1 캜 / min to 4 캜 / min and in the temperature range of the sintering temperature to 1100 캜 By setting the cooling rate at 6 DEG C / min or more, the second granular phase was dispersed and the average area of the second granular phase was fine to less than 0.2 mu m < ^{2 &} gt ;. Further, the second grain boundary phase was dispersed in 900 or more within a range of arbitrary 53 x 53 탆 ² . By having such a structure, H _cJ can be improved while maintaining a high B _r and a high H _k / H _cJ , as revealed in Example 1. [

On the other hand, in the ferrite sintered magnet of the comparative example, since the heating rate and the rate of temperature decrease were not suitable in the sintering step, the second granular phase became a ubiquitous structure and the average area of the second granular phase was as large as 0.2 탆 ² or more. In addition, within the range of arbitrary 53 x 53 mu m < ^{2 &} gt ;, only less than 900 second grain boundary phases were dispersed. In such an organization, as shown in Example 1, H _cJ can not be improved.

Example 3

The ferrite sintered magnets of sample Nos. 7 to 12 of Example 2 were subjected to FE-SEM (field emission scanning electron microscopy) and EDX (energy dispersive X-ray spectroscopy) The composition of the whole of the drawing, the composition of optional columnar phases (two portions) and the composition of the optional second grain boundary phase were analyzed. The results of the composition analysis are shown in Table 5. The values shown in Table 5 are all represented by atomic ratios (%). The beam diameter was 100 탆 for the entire composition and the beam diameter was 1 탆 for the main phase and the second grain boundary phase. In the table, " N.D. "

[Table 5]

As can be seen from Table 5, the second grain boundary phase necessarily contains Si and Ca, and the total amount of Si and Ca occupies at least 50 atomic% of the entire second grain boundary phase. Fe and a small amount of La were contained in the second grain boundary phase.

Example 4

0, z = 0.2 and n = 4.8 in the composition formula Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z , and the addition amounts of SiO ₂ , CaCO ₃ Ferrite sintered magnets of Samples Nos. 13 to 16 were obtained in the same manner as in Example 1, except that the addition amount (in terms of CaO conversion), the heating rate, the cooling rate and the sintering temperature were used. The results of measurement of B _r , H _cJ and H _k / H _cJ of the obtained ferrite sintered magnet are shown in Table 6.

[Table 6]

[Table 6 (continued)]

This embodiment is an example in which the content (z) of Co is 0.2 (z = 0.3 in Examples 1 to 3). As can be seen from Table 6, even when the content (z) of Co is changed, the ferrite sintered magnet of the present invention has a temperature raising rate of 1 占 폚 and a temperature decreasing rate of 10 占 폚, It is possible to improve H _cJ and H _k / H _cJ substantially without lowering B _r as compared with the ferrite sintered magnet according to the comparative example in which the heating rate is 7 ° C and the cooling rate is 4 ° C.

These ferrite sintered magnets are composed of the first granular phase existing between the main phase and the two main phases and the second granular phase existing between the two main phases, It is confirmed that the second grain boundary phase is scattered on an arbitrary section with the grain boundary phase and the average area of the second grain boundary phase is less than 0.2 占 퐉 ² .

Example 5

The composition formula _{Ca 1 -x- y La x A y} Fe 2n - in the _{z Co z, x = 0.5,} y = 0.05, z = 0.3 and n = 5.3 and, Ba and / or Sr as the element A as shown in Table 7 The same procedure as in Example 1 was carried out except that SiO ₂ addition amount, CaCO ₃ addition amount (CaO conversion value), heating rate, reduction temperature and firing temperature shown in Table 7 were used and ferrite of samples No. 17 to 22 A sintered magnet was obtained. Table 7 shows the results of measurement of B _r , H _cJ and H _k / H _cJ of the resulting ferrite sintered magnet.

[Table 7]

[Table 7 (continued)]

This embodiment is an embodiment in which the element A (y = 0.05) is contained. As can be seen from Table 7, even when the ferrite sintered magnet of the present invention contains element A, the rate of temperature rise is set to 1 占 폚 and the rate of temperature decrease to 10 占 폚, , H _cJ and H _k / H _cJ can be improved without substantially decreasing B _r as compared with the ferrite sintered magnet according to the comparative example in which the heating rate is 7 ° C and the cooling rate is 4 ° C.

These ferrite sintered magnets are composed of the first granular phase existing between the main phase and the two main phases and the second granular phase existing between the two main phases, It is confirmed that the second grain boundary phase is scattered on an arbitrary section with the grain boundary phase and the average area of the second grain boundary phase is less than 0.2 占 퐉 ² .

[Industrial applicability]

The ferrite sintered magnet according to the present invention can be suitably used for automobile electric parts such as various motors, generators, and speakers, and parts for electric devices. Particularly, the ferrite sintered magnet can contribute to reduction in size, weight and high efficiency of these parts.

Claims (7)

A main phase composed of a ferrite having a hexagonal M type magnetoplumbite structure and a first grain boundary phase existing between two columnar phases and a second phase boundary between the two main phases, having a second grain boundary phase existing between the at least three circumferentially, in any cross section, and the second grain boundary phase is dispersed (散在) and have an average area of the second grain boundary phase 0.2㎛ ² is less than the ferrite sintered A method of manufacturing a magnet,
In the general formula: Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z , which represents the atomic ratio of the metal elements of elements A, Ca, La, Ba and / or Sr,
Wherein 1-xy, x, y and z, and n representing the mole ratio,
0.3? 1-xy? 0.65,
0.3? X? 0.65,
0? Y? 0.2,
0.25? Z? 0.65, and
4.5? N? 7
To prepare a raw material powder;
A calcination step of calcining the raw material powder to obtain a calcined body;
A pulverizing step of pulverizing the calcined body to obtain a powder;
A molding step of molding the powder to obtain a molded body; And
A sintering step of sintering the molded body to obtain a sintered body,
/ RTI >
0% by mass to 1.8% by mass SiO ₂ and 0% by mass to 2% by mass CaCO ₃ in terms of CaO are added to the calcined body after 100% by mass of the calcined body after the calcining step , And
In the firing step, the temperature raising rate in the temperature range of 1100 ° C to the firing temperature is set to 1 ° C / min to 4 ° C / min, and the temperature decreasing rate in the temperature range of firing temperature to 1100 ° C is set to 6 Lt; RTI ID = 0.0 > C / min / min. ≪ / RTI > The method according to claim 1,
Wherein the amount of SiO ₂ added is 1% by mass to 1.8% by mass, and the amount of CaCO ₃ added is 1% by mass to 2% by mass in terms of CaO. 3. The method of claim 2,
Wherein the amount of the SiO ₂ added is 1.1% by mass to 1.6% by mass, and the amount of CaCO ₃ added is 1.2% by mass to 2% by mass in terms of CaO. 4. The method according to any one of claims 1 to 3,
Wherein the second granular phase is present in an amount of not less than 900 in a range of 53 x 53 mu m ² of an arbitrary cross section. A columnar phase composed of ferrite having a hexagonal M type magnetron plumbite structure, a first granular phase existing between the two columnar phases and a second granular phase existing between the three or more columnar phases, Wherein the second granular phase is dispersed and the average area of the second granular phase is less than 0.2 占 퐉 ² . 6. The method of claim 5,
Wherein the ferrite sintered magnet comprises:
Ca _{1 -x- y} La _x A _y Fe _{2n - z} Co _z representing atomic ratios of metal elements of elements A, Ca, La, Ba and / or Sr, , x, y and z, and n representing the molar ratio,
0.3? 1-xy? 0.75,
0.2? X? 0.65,
0? Y? 0.2,
0.25? Z? 0.65, and
Fe and Co, and 0 mass% to 1.8 mass% SiO ₂ , which are Ca, La, Ba and / or Sr, satisfying 3? N? 6. The method according to claim 5 or 6,
Wherein the second grain boundary phase is present in at least 900 areas within a range of 53 x 53 mu m ² of an arbitrary section.

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